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Newman Projections
In the 37th Millenium, the forces of chaos struck again.You cannot grasp the true form of chaos's attacks. In order to find a way to grasp the true form, Newman Projections were created by mah boi Newman. What are Newman Projections? Shit's 3D, and shit can rotate. This creates a variety of possible three-dimensional shapes called conformations. Some are higher in energy, some are lower in energy. In order to grasp their true form, one must depict them using Newman Projections. If we are looking at the side of a molecule, like you are used to, we get a wedge/dash formula for depicting the molecule. We use dashes and big bois to depict shape. But chaos is crafty, so they started rotating there stuff. If we rotate the image 45 degrees, we get the sawhorse formula. Further rotating it so that we are at a 90 degree rotation from the Wedge/dash formula gives us the Newman Projection. Here, the two carbons are overlapping. Conformational Analysis Consider the two hydrogens on the left side of the staggered conformation(you will know what that is in a few minutes) They appear to be separated by an angle of 60 degrees right? This angle is called the dihedral angle(Or torsional angle). This angle changes as the C-C bond rotates, and there are infinity possible conformations because of this. However, only two of them matter. The Staggered conformation is the lowest in energy, while the eclipsed conformation(when atoms start overlapping on the projection) are the highest in energy. In the case of ethane, the differences in energy between the two is 12 kJ/mol. Degeneracy: Anime Actually if you call two conformations degenerate, it means they have the same energy. In the case of ethane, all staggered conformations are degenerate. Torsional Strain: Torsional strain causes the difference in energy between staggered and eclipsed conformations. Torsional strain is believed to be the energy in a molecule due to the repulsion of eclipsing sigma bonds. Also worth noting is Steric Strain, which is the energy in a molecule due to the repulsion between atoms that are close in space lets look at butane Now that thats done, lets talk about conformational analysis of Butane. If you look at its energies as it rotates, you will see that the eclipsed conformation when it has dihedral angle 0 is higher than its other eclipsed conformation energies. This means its three eclipsed conformations are not degenerate. Similarily, one of the three staggered conformations is lower in energy than the other two. Anti Confns The conformation with a dihedral angle of 180 is called the anti conformation, and represents the lowest energy conformation of butane. Specifically, anti means two things that are 180 degrees apart. You can see the anti conformation of butane at the right end of the above image, where the methyl groups are 180 degrees apart, meaning they are the maximum distance from each other. When they are closer, their electron clouds repel each other, increasing energy. This can result in Gauche Interactions ''Gauche ''means that two non-hydrogen substituents that are 60 degrees apart from one another on adjacent carbon atoms. This would be the middle two conformations in the image above, and they are obviously called gauche conformations. Now lets look at the three eclipsed conformations. One is higher energy than the other two, and that one is the one where the methyl groups eclipse eachother(left conformation in the image above)